Abstract
The reuse of construction demolition waste and rubber waste has been a key challenge in recent decades due to the decrease in natural material resources and the huge amounts of abundantly available waste. When recycled aggregates (RCA) and crumb rubber (RBR) are used together as partial substitutions for coarse and fine aggregates, respectively, in concrete, it leads to a decrease in the compressive strength when compared to natural aggregate concrete, so it is needed to construct models that can predict the strength before using them. In this paper, response surface methodology was utilized to develop predictive models for the influence of the combined incorporation of RCA and RBR in concrete on the compressive strength. The predictions were based on the results of 100 various concrete mixes obtained from previous works and from the literature. The variables included w/c ratio (0.39 and 0.5), RBR replacement (0% to 40%), levels of RCA replacement (0% to 100%), and durations of 7 and 28 days. The compressive strength was taken as a response. All models and their terms were validated using various statistical tests. The results showed that linear and quadratic models and their terms were significant, and can be utilized for the prediction of the compressive strength with less error